Objective : To investigate the scientific bases for the traditional use of Stachytarpheta angustifolia. Methods: In vitro antibacterial activity of the aqueous and ethanol extract of the plant was investigated using the agar cup plate diffusion method. Results: The ethanol extract of the plant shoued antibacterial activity against Escherichia coli , Streptococcus faecalis , Shigella dysenteriae ,Staphylococcus aureus ( S. Aureus ), Salmonella sp. , Pseudomonas aeruginosa and Neisseria gonorrhoeae, while the water extract was active against Escherichia coli, Streptococcus faecalis, Shigella dysenteriae, Staphylococcus aureus and. Pseudomonas aeruginosa. The ethanol extract exhibited higher antibacterial activity than the water extract. The minimum inhibitory concentration (MIC) and minimum bacterwidal concentration ( M BC ) of the ethanol extract were 0.65 mg / ml and 0.85 mg / ml , respectively, against S. Aureus. Treatment of the extract at higher temperature, 60 ℃ increased the sensitivity of the test organisms to the plant extract. Phytochemical analysis indicated that the plant possesses tannins, saponins as well as phenols. Conclusion: A scientific basis exists that the plant possesses antibacterial activity and it could be a probable source of therapeutic agent.